The Percy Jackson series is set in the regular modern world, except that the ancient Greek gods are real. Their home, Mount Olympus, hovers over the Empire State Building in Manhattan. All of the Greek gods, including minor deities, can and do have children with humans; these children are demigods. Demigods inherit powers from their divine parents. The three most powerful gods, Zeus, Poseidon, and Hades, are not meant to have children as their offspring tend to be too powerful and dangerous. Perseus “Percy” Jackson is a son of Poseidon who first learns of his demigod status at the age of 12. He is able to control water, breathe underwater, and communicate with horses and sea creatures. All demigods run the risk of being attacked by monsters from Greek mythology, but Percy is particularly at risk because his father is so powerful. Percy attends Camp Half-Blood, a training camp for demigods. There, he meets Annabeth Chase, daughter of Athena, who later becomes his girlfriend. He also learns that his long-time friend, Grover Underwood, is actually a satyr who has been tasked with protecting him.

In Percy’s world, all deities, monsters, and magical creatures can hide in plain sight using the Mist, a magical glamor that prevents people from seeing anything out of the ordinary unless they are paying very close attention.